This application claims priority from Korean Patent Application No. 2002-48393 filed on Aug. 16, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a flash controlling apparatus, and more particularly, to an apparatus for controlling the operation of a flash device of a camera.
2. Description of the Related Art
It has been proposed to implement a flash controlling apparatus for a camera having a control voltage generator which produces a control voltage that increases linearly with time, so that the flash is terminated when the linearly increasing control voltage crosses a reference voltage threshold. However, such an apparatus would emit too much light if the distance between an object OB and the camera is short and/or if an ambient illumination intensity is high, if it is designed to emit an appropriate amount of light when the distance between an object OB and the camera is long and/or if an ambient illumination intensity is low. In other words, referring to FIG. 1, due to the linear characteristics of the control voltage SPS over time, a light emitting time TS (produced for short distances and/or high ambient light) is longer than it ought to be when a light emitting time TL (produced for long distances and/or low ambient light) is appropriate. To solve this problem, if the inclinations of an SPPS characteristic line for near objects or relatively high ambient light levels and an SPSL characteristic line for far objects or relatively low ambient light levels are increased, the light emitting time TL is shorter than required, although the light emitting time TS is then appropriate. Consequently, in the proposed flash controlling apparatus, the amount of light emitted from the flash device cannot be appropriately controlled according to the distance between the object and the camera and the intensity of the ambient illumination.
The present invention provides a flash controlling apparatus which can more uniformly control the amount of flash light emission regardless of the distance between an object and a camera and the intensity of an ambient illumination.
According to an aspect of the present invention, there is provided a flash controlling apparatus including a light receiving unit PS, a current-to-voltage converter IVC, a comparator CR, and a micro-controller MC. The light receiving unit PS generates a current signal corresponding to the flash intensity of a camera. The current-to-voltage converter IVC converts the current signal received from the light receiving unit PS into a voltage signal SPS. The comparator CR compares the voltage signal SPS with a reference voltage VREF to obtain a resultant logic signal SCOM. The micro-controller MC controls the operation of the current-to-voltage converter IVC and controls the operation of a flash device of the camera according to the resultant logic signal SCOM received from the comparator CR. The voltage signal SPS from the current-to-voltage converter IVC has the characteristics of a logarithmic function with respect to time.
In the flash controlling apparatus according to the present invention, since the voltage signal SPS from the current-to-voltage converter IVC has the characteristics of a logarithmic function with respect to time, the light-emitting time TS when an object is close to a camera and/or when an ambient illumination is high can be reduced relative to that of a conventional flash controlling apparatus while the light-emitting time TL when an object is far from a camera and/or when an ambient illumination is low can be made similar to that of the conventional flash controlling apparatus. Accordingly, the amount of light emitted from the flash device can be more appropriately controlled according to the distance between an object and a camera and the intensity of an ambient illumination.